ROCHESTER, N.Y. — Evelyn Rose, 4, of Brighton faced a tough choice in the Baby Lab at the University of Rochester: eat a luscious-looking marshmallow in a yellow dessert cup or wait a few minutes and be rewarded with a second marshmallow.

Evelyn decided to wait, but it wasn't easy.

She pretended to clop like a horse, covered the treat with her hands, bounced it like a ball and even licked it — all in an attempt to restrain herself.

In the end, Evelyn held out for an extraordinary 15 minutes and was rewarded with more marshmallows.

"I knew she would wait," said Evelyn's mom, Meghann Rose, "but I was surprised by how long she waited."

So were the University of Rochester researchers conducting this groundbreaking experiment that was published in Cognition, an international journal of cognitive science research.

In the study of 28 3- to 5-year-olds, researchers found that children like Evelyn who experienced reliable interactions with a researcher immediately before the marshmallow experiment waited on average four times longer to eat the marshmallow than children who had an unreliable interaction.

"Astounding" is the word that Richard Aslin, the William R. Kenan professor of brain and cognitive sciences at UR, uses to describe the results of the robust study that demonstrates that the ability to delay gratification is influenced as much by the environment as by innate ability.

If the marshmallow task sounds familiar, it's because it is not a new concept. But the work of Aslin, lead author Celeste Kidd and co-author Holly Palmeri has entirely new implications.

The original marshmallow studies were conducted at California's Stanford University in the 1960s by Walter Mischel. Those famous studies about differences in individuals' abilities to delay gratification correlated strongly with success in later life, such as higher SAT scores and lower rates of substance abuse.

What the studies did not clearly show, though, is why children waited, or did not wait, to eat marshmallows.

"The original marshmallow papers mentioned that environmental reasons could play a role in decision-making, but the idea was not followed through," Kidd said. "Instead, it was assumed children who did not delay gratification had poor impulse control."

It was also in California where the seeds for UR's new twist on the marshmallow studies took root.

Kidd was volunteering at a homeless shelter in Santa Ana, Calif., in 2009 when she noticed a little girl, about 3 years old, with a lollipop.

"That looks delicious," Kidd said to her as the little girl was about to put the tasty treat in her mouth.

Yet before the little girl could taste it, an older boy grabbed the lollipop and ran away in "one swift action."

Kidd braced herself for the little girl's tears, but, shockingly, they never came.

"She didn't respond at all," said Kidd, a doctoral candidate in brain and cognitive sciences at UR. "I thought this was very strange and that maybe she was lacking something; children should be upset when things are taken away, right?"

From then on, Kidd noticed that most children in the shelter did not get upset when other children regularly took their toys or food.

She began to realize it was not because they lacked emotion, but because this was their norm.

"If you're in a place where things get taken all of the time, then you get used to things being taken away," Kidd said.

"It started me down this line of wanting to look at kids' beliefs on reliability related to the marshmallow test."

And so from an observation about a lollipop, a new study about marshmallows was born.

In UR's marshmallow studies, the 28 children were randomly assigned to two groups: reliable and unreliable.

In both groups, the children were given an arts and crafts project to work on when they arrived.

In the unreliable group, the children were provided a cup of dingy, used crayons and told that if they could wait, the researcher (Palmeri) would return shortly with a big set of "better" art supplies for their project.

After 2½ minutes, the researcher returned empty-handed.

Next the child was offered a little sticker to decorate their project and was told that if he or she could wait before using it, the researcher would return with a large selection of "better" stickers. After the same wait, the researcher again returned empty-handed.

The reliable group experienced the same setup, but the researcher (also Palmeri) always returned with the promised materials — a teeming assortment of new art supplies and a large assortment of fun stickers.

The marshmallow task followed, with the explanation that the child could have one marshmallow immediately or wait for the researcher to return with two.

Almost on cue, the children in the unreliable group knew the researcher wouldn't fulfill her promise and they ate their marshmallow quickly, as opposed to those in the reliable group who knew they would be rewarded as they had been in the past by waiting.

The average time a child in the reliable group waited before eating the marshmallow was 12 minutes, versus 3 minutes in the unreliable group.

"I think the reliability played a big part in her waiting as long as she did," Rose said about her daughter. "She was having fun and knew she was being rewarded by the caregiver. Kids really do watch what adults do more than we think they do."

Kidd is excited about the implications the study inspired by a little girl at a homeless shelter might have in many fields affecting children, such as education.

"I hope people will be more careful to assume that a lack of restraint is a personality defect," Kidd said.

"A lack of impulse control is not necessarily the reason kids make the choices they do."